Samar Badawi and Nassima al-Sadah were detained in July 2018, along with more than a dozen other activists, on suspicion of harming Saudi interests, a move that drew international condemnation.
The Saudi government's media office did not immediately respond to a Reuters request for comment. Few details have been provided by authorities on the charges against the women or on sporadic trials that have been closed to the public.
Their release follows that of prominent activist Loujain al-Hathloul in February who had served half of her custodial sentence on broad cybercrime and counterterrorism charges. She still faces a five-year travel ban.
Human Rights Watch welcomed the report by ALQST on Twitter of the release of Badawi and Sadah: "These brave women should have never been detained in the first place. They should have been appreciated for leading change in Saudi Arabia."
Badawi received the United States' International Women of Courage Award in 2012 for challenging the Saudi male guardianship system, and was among the first women who signed a petition calling on the government to allow women to drive and to vote and run in local elections.
Sadah, from the restive Shi'ite-majority Qatif province, has also campaigned to abolish the guardianship system.
CRACKDOWN
The women's rights activists were detained before and after the kingdom in 2018 lifted a ban on women driving as part of social reforms that have been accompanied by a crackdown on dissent that has also netted clerics and intellectuals.
Badawi's former husband is serving a 15-year jail sentence for human rights activism. Her brother Raif Badawi, a prominent blogger, is serving a 10-year sentence on charges of insulting Islam and for cyber crime.
US President Joe Biden's administration has taken a tough stance over Saudi Arabia's human rights record, which came under the spotlight after the October 2018 murder of prominent Saudi journalist Jamal Khashoggi in the kingdom's Istanbul consulate.
Washington in February released an intelligence report implicating de facto ruler Crown Prince Mohammed bin Salman in Khashoggi's killing. The prince denies any involvement.
In April, the State Department voiced concern about the sentencing of a Saudi aid worker by a counterterrorism court to 20 years in prison followed by a 20-year travel ban.